Infantino faced calls to resign over his failed attempt to bring private investors into a new commercial entity holding rights linked to competitions including FIFA's flagship tournament.
Sheikh Salman joined the presidents of other regional bodies UEFA (for Europe) and CONCACAF (North America, Central America, Caribbean) to pen an open letter criticising the FIFA president's conduct.
Football Australia (FA) threw its support behind the Asian confederation when the controversy exploded in August, calling for "clear and credible action that continues to strengthen governance, transparency and accountability within FIFA".
FA has been approached for its response to the announcement of the AFC's support.
Infantino, who apologised over the handling of the FIFA Forward Enterprise (FFE) project at a FIFA Council meeting in Zurich this month, is up for re-election in March next year and the support of the Asian bloc could prove crucial.
Speaking at the AFC's extraordinary congress in Tokyo on Friday, Sheikh Salman said he had ironed out his differences with Infantino.
"We re-affirm our full commitment, of course, to supporting you and your leadership as you seek a new mandate as FIFA president," he said in comments directed at Infantino, who was present at the meeting.
"I want to make it clear: yes, we had some issues we spoke about in the past but let's not relate the two things together.
"We need to move forward. And we believe football is strongest when we work together with a shared vision and a common purpose."
While Africa has also backed Infantino's re-election, he continues to face opposition from European soccer's governing body.
UEFA has sent a letter to FIFA seeking answers about his presidency, including questions over the FFE project and the FIFA Peace Prize.
Infantino, 56, is seeking a fourth term until 2031 and potential candidates must submit their nominations by November 18.
Several key AFC members, including Saudi Arabia and Qatar, have already publicly declared their support for Infantino.
Japan Football Association President Tsuneyasu Miyamoto said on Friday the association was looking to align with the AFC but that they had not made a decision.
He was also unsure whether all 47 members of the confederation were united in supporting the Swiss-Italian administrator.
"I don't think the AFC members' opinions are all aligned together, but I believe the AFC and FIFA have been holding meetings on an ongoing basis," Miyamoto said.
